A medical imaging marker is often used for providing accurate positional information for imaging data when a patient is imaged by means of a medical imaging apparatus such as CT or MRI.
More specifically, when a medical treatment is carried out based on the results of image diagnosis or simulation performed with the use of medical three-dimensional image information acquired through imaging by means of an imaging apparatus such as CT or MRI, a treatment position and a treatment direction specified on an image should be mapped onto an actual object.
Therefore, a reference position and a direction should be able to be correctly defined in a three-dimensional image formed, for example, based on CT image data acquired through the CT imaging. For the correct definition of the reference position in the image, the medical imaging marker should be present in the image.
The medical imaging marker is typically used to identify a reference point in the acquired three-dimensional image. For identification of a center point of the marker, the marker is preferably imaged as having a round shape when the three-dimensional image is viewed in any angular direction. For this reason, a spherical marker is proposed as the medical imaging marker (see, For example, Patent Document 1).    Patent Document 1: JP-A-2006-141640